The present invention is directed generally to electrical connectors of a type providing protection from electromagnetic interference (EMI). More particularly, the invention is directed to a multiple contact filter connector capable of conducting high RF currents and which includes improved filter network and contact assemblies which provide a full range of EMI protection while accommodating a high density contact array and allowing the contacts to be readily inserted into and removed from the connector.
In numerous applications where long unshielded cable runs enter a shielded housing containing circuitry sensitive to extraneous signals picked up by the cable, it is necessary to provide electrical filter networks as an integral part of a connector to suppress transient and other undesired signals, such as EMI, which may otherwise exist on circuits interconnected by the connector. An illustrative prior art filter connector used in such applications is shown and described in Tuchto et al, U.S. Pat. No. 3,854,107, assigned to the same assignee as the present invention.
The filter connector illustrated in the aforementioned Tuchto et al patent includes a dielectric body having a plurality of through bores, a like plurality of filter contacts supported within the bores, and a thin conductive foil ground plate. Each filter contact includes a filter network comprising multiple concentric filter elements coaxially disposed about a reduced diameter portion of the contact and a ground electrode outer coating forming a pi network filter. The bores and filter contacts are so dimensioned that the contacts may be inserted into and removed from the bores with the ground electrodes contacting the thin foil ground plate through wiping action.
While multiple contact filter connectors of the foregoing variety have proven successful when used to conduct relatively low RF currents of approximately one-quarter ampere, they have not been suitable for conducting high RF currents of, for example, three amperes, because the ground plates are thin. The thin ground plates cannot adequately dissipate the extreme heat generated by high current conduction, causing the connectors to overheat and, ultimately, fail. Additionally, since the filter networks and contacts are integral units, there is always the possibility of damage to the rather fragile networks during removal and insertion of the contacts. Lastly, full range EMI protection is not possible due to the inherent low filter capacitance afforded by the multiple coaxial layer network construction. To increase the filter capacitance, it would be necessary to lengthen the contacts, and thus the connector, to such an extent as to limit the useful applications.